Conventional fireworks and display rockets are driven by a powder mixture of potassium nitrate, charcoal, and sulphur. Smaller rockets employ a mixture of potassium perchlorate and an alkali metal salt of an aromatic carboxylic acid. This mixture is conventionally modified by the addition of a liquid binder, for example a mineral or vegetable oil, which also reduces the sensitiveness of the composition to impact or friction. Other proposals have been that the composition should contain liquid components that react on mixing to form a solid polymeric binder--see, for example, British Patent Specification No. 1202390. In all such cases, however, the resulting composition is no longer free-flowing and so the rocket casing or other container may not be filled using the advantageous funnel and rammer technique employing a powder dispenser.